1. Field of the Invention
This invention relates to a developing device used in an image forming apparatus, such as a copier, a laser-beam printer or the like, for forming an electrostatic latent image on an image carrying member and for developing the image. The invention also relates to a process cartridge including the developing device.
2. Description of the Related Art
Heretofore, when conveying toner from a toner receptacle housing a developer to a developing chamber, in a configuration as shown in FIG. 1, a toner receptacle 3 is situated at a position higher than a developing chamber 5 including a developing roller 6. Since toner T spontaneously drops into the developing chamber 5 by its own weight when a seal 20 is removed, it is not necessary to provide a toner stirring means within the toner receptacle 3. However, when the toner receptacle 3 is disposed at the same height as the developing chamber 5, as shown in FIG. 2, all the toner T within the toner receptacle 3 does not move to the developing chamber 5 merely by removing the seal 20. Hence, a toner stirring means 4 is disposed within the toner receptacle 3, and the toner is stirred by rotating the toner stirring means 4 to convey the toner to the developing chamber 5.
However, there exist the following problems in the conventional approach as described above. That is, if the toner becomes agglomerated due to various conditions, such as, vibration during the transportation of its receptacle, being undisturbed for a long period, temperature rise or the like, the load resistance of the agglomerated toner becomes large. As a result, a state arises in which the toner stirring means does not easily move. If a driving force is applied to the toner stirring means in this state, the following problems arise:
(1) A tooth-skipping phenomenon is produced between transmission gears which transmit a driving force to the toner stirring means. PA1 (2) The load for a driving source (a motor) in the main body becomes excessive, which causes stoppage and breakdown of the driving source. PA1 (3) The toner stirring means is plastically deformed due to the load of the agglomerated toner and a sliding contact member does not uniformly slidably contact the inner wall of the toner receptacle, and the toner is not sufficiently stirred and conveyed. PA1 (4) The stirring means is deformed by a bending force applied thereto due to the load of the agglomerated toner, and the apparent total length of the stirring means in the axial direction becomes short. The stirring means is thereby detached from bearings or the like which support the stirring means, and the toner is not sufficiently stirred and conveyed.
The picture quality of the toner image thus deteriorates due to the problems as described above.